1. Field of the Invention
Embodiments of the present invention generally relate to a method for reducing particle deposition and cleaning a chamber while processing a substrate. More specifically, embodiments of the present invention relate to an in situ chamber clean with an inert hydrogen helium mixture during wafer processing.
2. Description of the Related Art
During chip packaging, metal layers are used for connecting solder material to bond pads that are electrically connected to semiconductor devices. Generally, incoming wafers for under-bump metallization (UBM) processes consist of metal pads embedded in a polymer passivation layer, such as a polyimide layer. The metal pads, such as aluminum pads, must be cleaned prior to UBM to remove any native oxide, such as aluminum oxide, from the surface of the metal pads.
FIG. 1A is a prior art schematic view of a packaging preclean process chamber 100. Currently, etching processes are used to remove the native oxide 114 from the surface of the aluminum pads 112. Etching processes generally utilize a halogen plasma 106, such as an argon plasma, to bombard the surface of a substrate 110 with ions to sputter (remove) undesired material present on the surface of the substrate 110. The etching removes native oxide 114, which generally reduces electrical conductivity, from the surface of the aluminum pads 112 but also sputters 118 the polymer layer 116 which re-deposits on interior surfaces 104 of the semiconductor processing chamber kit 102. The re-deposited polymer 108 on the interior surfaces 104 increases the presence of particles in the chamber which may lead to undesirable contamination of the substrate 110 and increase the defectivity of the packaging preclean process.
Generally, the polymer sputtered on the interior surfaces of the chamber kit is pasted over with an aluminum paste to reduce the presence of particle contaminants in the chamber. However, aluminum pasting in the chamber is time consuming and decreases throughput because a substrate is generally not present in the chamber during the pasting process. Therefore, it is desirable to reduce the amount of polymer re-deposited on the interior surfaces of the chamber. Providing oxygen plasma to the chamber to perform an ashing process is effective at removing the polymer from the interior surfaces of the chamber but the presence of oxygen in the chamber will cause oxidation of the metal pad, creating undesirable native oxide thereon as previously discussed. Therefore, a substrate cannot be processed while performing an ashing process, which reduces throughput.
Accordingly, what is needed in the art is a method of reducing polymer deposits on the interior surfaces of a processing chamber that does not promote the formation of native oxide and reduces the frequency of aluminum pasting to cover the re-deposited polymer on the interior surfaces of the chamber.